Stitch MCP — Update Design System

Updates an existing Stitch Design System. Use this to modify theme properties, design tokens, or style guidelines without creating a new design system.

Critical prerequisite

Only use this skill when the user explicitly mentions "Stitch".

You must have the design system's asset name before calling this. If you don't have one:

• List existing design systems via stitch-mcp-list-design-systems
• Or use the name returned from stitch-mcp-create-design-system

When to use

• User wants to modify colors, fonts, or roundness of an existing design system
• After reviewing a design system and wanting to adjust specific properties
• Updating design tokens after a brand refresh

Call the MCP tool

{
  "name": "update_design_system",
  "arguments": {
    "name": "assets/15996705518239280238",
    "projectId": "3780309359108792857",
    "designSystem": {
      "displayName": "SaaS Dashboard Theme v2",
      "theme": {
        "colorMode": "DARK",
        "headlineFont": "GEIST",
        "bodyFont": "GEIST",
        "labelFont": "GEIST",
        "roundness": "ROUND_TWELVE",
        "customColor": "#818CF8"
      }
    }
  }
}

Parameter reference

Three sibling top-level arguments — name is not nested inside designSystem:

designSystem — {displayName, theme} only

updatedesignsystem takes the asset id prefixed (assets/159967...), while applydesignsystem takes the same id bare. Two tools, same identifier, different formats.

designTokens and styleGuidelines are not accepted — the live API has no such fields on DesignSystem. Don't send them.

Note: This is a full replacement, not a merge. Include all theme fields you want to keep, not just the ones you're changing.

Output

Returns the updated Asset object:

{
  "name": "assets/15996705518239280238",
  "displayName": "SaaS Dashboard Theme v2",
  "designSystem": { ... }
}

After updating

• Offer: "Re-apply this updated design system to existing screens?" → stitch-mcp-apply-design-system
• Screens generated before the update won't automatically reflect changes — they need to be re-applied